x86/ia32/ia32_signal.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  *  linux/arch/x86_64/ia32/ia32_signal.c
0004  *
0005  *  Copyright (C) 1991, 1992  Linus Torvalds
0006  *
0007  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
0008  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
0009  *  2000-12-*   x86-64 compatibility mode signal handling by Andi Kleen
0010  */
0011
0012 #include <linux/sched.h>
0013 #include <linux/sched/task_stack.h>
0014 #include <linux/mm.h>
0015 #include <linux/smp.h>
0016 #include <linux/kernel.h>
0017 #include <linux/errno.h>
0018 #include <linux/wait.h>
0019 #include <linux/unistd.h>
0020 #include <linux/stddef.h>
0021 #include <linux/personality.h>
0022 #include <linux/compat.h>
0023 #include <linux/binfmts.h>
0024 #include <linux/syscalls.h>
0025 #include <asm/ucontext.h>
0026 #include <linux/uaccess.h>
0027 #include <asm/fpu/signal.h>
0028 #include <asm/ptrace.h>
0029 #include <asm/ia32_unistd.h>
0030 #include <asm/user32.h>
0031 #include <uapi/asm/sigcontext.h>
0032 #include <asm/proto.h>
0033 #include <asm/vdso.h>
0034 #include <asm/sigframe.h>
0035 #include <asm/sighandling.h>
0036 #include <asm/smap.h>
0037
0038 static inline void reload_segments(struct sigcontext_32 *sc)
0039 {
0040     unsigned int cur;
0041
0042     savesegment(gs, cur);
0043     if ((sc->gs | 0x03) != cur)
0044         load_gs_index(sc->gs | 0x03);
0045     savesegment(fs, cur);
0046     if ((sc->fs | 0x03) != cur)
0047         loadsegment(fs, sc->fs | 0x03);
0048     savesegment(ds, cur);
0049     if ((sc->ds | 0x03) != cur)
0050         loadsegment(ds, sc->ds | 0x03);
0051     savesegment(es, cur);
0052     if ((sc->es | 0x03) != cur)
0053         loadsegment(es, sc->es | 0x03);
0054 }
0055
0056 /*
0057  * Do a signal return; undo the signal stack.
0058  */
0059 static bool ia32_restore_sigcontext(struct pt_regs *regs,
0060                     struct sigcontext_32 __user *usc)
0061 {
0062     struct sigcontext_32 sc;
0063
0064     /* Always make any pending restarted system calls return -EINTR */
0065     current->restart_block.fn = do_no_restart_syscall;
0066
0067     if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
0068         return false;
0069
0070     /* Get only the ia32 registers. */
0071     regs->bx = sc.bx;
0072     regs->cx = sc.cx;
0073     regs->dx = sc.dx;
0074     regs->si = sc.si;
0075     regs->di = sc.di;
0076     regs->bp = sc.bp;
0077     regs->ax = sc.ax;
0078     regs->sp = sc.sp;
0079     regs->ip = sc.ip;
0080
0081     /* Get CS/SS and force CPL3 */
0082     regs->cs = sc.cs | 0x03;
0083     regs->ss = sc.ss | 0x03;
0084
0085     regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
0086     /* disable syscall checks */
0087     regs->orig_ax = -1;
0088
0089     /*
0090      * Reload fs and gs if they have changed in the signal
0091      * handler.  This does not handle long fs/gs base changes in
0092      * the handler, but does not clobber them at least in the
0093      * normal case.
0094      */
0095     reload_segments(&sc);
0096     return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
0097 }
0098
0099 COMPAT_SYSCALL_DEFINE0(sigreturn)
0100 {
0101     struct pt_regs *regs = current_pt_regs();
0102     struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
0103     sigset_t set;
0104
0105     if (!access_ok(frame, sizeof(*frame)))
0106         goto badframe;
0107     if (__get_user(set.sig[0], &frame->sc.oldmask)
0108         || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
0109         goto badframe;
0110
0111     set_current_blocked(&set);
0112
0113     if (!ia32_restore_sigcontext(regs, &frame->sc))
0114         goto badframe;
0115     return regs->ax;
0116
0117 badframe:
0118     signal_fault(regs, frame, "32bit sigreturn");
0119     return 0;
0120 }
0121
0122 COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
0123 {
0124     struct pt_regs *regs = current_pt_regs();
0125     struct rt_sigframe_ia32 __user *frame;
0126     sigset_t set;
0127
0128     frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
0129
0130     if (!access_ok(frame, sizeof(*frame)))
0131         goto badframe;
0132     if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
0133         goto badframe;
0134
0135     set_current_blocked(&set);
0136
0137     if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
0138         goto badframe;
0139
0140     if (compat_restore_altstack(&frame->uc.uc_stack))
0141         goto badframe;
0142
0143     return regs->ax;
0144
0145 badframe:
0146     signal_fault(regs, frame, "32bit rt sigreturn");
0147     return 0;
0148 }
0149
0150 /*
0151  * Set up a signal frame.
0152  */
0153
0154 #define get_user_seg(seg)   ({ unsigned int v; savesegment(seg, v); v; })
0155
0156 static __always_inline int
0157 __unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
0158                 void __user *fpstate,
0159                 struct pt_regs *regs, unsigned int mask)
0160 {
0161     unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
0162     unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
0163     unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
0164     unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
0165
0166     unsafe_put_user(regs->di, &sc->di, Efault);
0167     unsafe_put_user(regs->si, &sc->si, Efault);
0168     unsafe_put_user(regs->bp, &sc->bp, Efault);
0169     unsafe_put_user(regs->sp, &sc->sp, Efault);
0170     unsafe_put_user(regs->bx, &sc->bx, Efault);
0171     unsafe_put_user(regs->dx, &sc->dx, Efault);
0172     unsafe_put_user(regs->cx, &sc->cx, Efault);
0173     unsafe_put_user(regs->ax, &sc->ax, Efault);
0174     unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
0175     unsafe_put_user(current->thread.error_code, &sc->err, Efault);
0176     unsafe_put_user(regs->ip, &sc->ip, Efault);
0177     unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
0178     unsafe_put_user(regs->flags, &sc->flags, Efault);
0179     unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
0180     unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
0181
0182     unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
0183
0184     /* non-iBCS2 extensions.. */
0185     unsafe_put_user(mask, &sc->oldmask, Efault);
0186     unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
0187     return 0;
0188
0189 Efault:
0190     return -EFAULT;
0191 }
0192
0193 #define unsafe_put_sigcontext32(sc, fp, regs, set, label)       \
0194 do {                                    \
0195     if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0])) \
0196         goto label;                     \
0197 } while(0)
0198
0199 /*
0200  * Determine which stack to use..
0201  */
0202 static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
0203                  size_t frame_size,
0204                  void __user **fpstate)
0205 {
0206     unsigned long sp, fx_aligned, math_size;
0207
0208     /* Default to using normal stack */
0209     sp = regs->sp;
0210
0211     /* This is the X/Open sanctioned signal stack switching.  */
0212     if (ksig->ka.sa.sa_flags & SA_ONSTACK)
0213         sp = sigsp(sp, ksig);
0214     /* This is the legacy signal stack switching. */
0215     else if (regs->ss != __USER32_DS &&
0216         !(ksig->ka.sa.sa_flags & SA_RESTORER) &&
0217          ksig->ka.sa.sa_restorer)
0218         sp = (unsigned long) ksig->ka.sa.sa_restorer;
0219
0220     sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
0221     *fpstate = (struct _fpstate_32 __user *) sp;
0222     if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
0223                       math_size))
0224         return (void __user *) -1L;
0225
0226     sp -= frame_size;
0227     /* Align the stack pointer according to the i386 ABI,
0228      * i.e. so that on function entry ((sp + 4) & 15) == 0. */
0229     sp = ((sp + 4) & -16ul) - 4;
0230     return (void __user *) sp;
0231 }
0232
0233 int ia32_setup_frame(int sig, struct ksignal *ksig,
0234              compat_sigset_t *set, struct pt_regs *regs)
0235 {
0236     struct sigframe_ia32 __user *frame;
0237     void __user *restorer;
0238     void __user *fp = NULL;
0239
0240     /* copy_to_user optimizes that into a single 8 byte store */
0241     static const struct {
0242         u16 poplmovl;
0243         u32 val;
0244         u16 int80;
0245     } __attribute__((packed)) code = {
0246         0xb858,      /* popl %eax ; movl $...,%eax */
0247         __NR_ia32_sigreturn,
0248         0x80cd,     /* int $0x80 */
0249     };
0250
0251     frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
0252
0253     if (ksig->ka.sa.sa_flags & SA_RESTORER) {
0254         restorer = ksig->ka.sa.sa_restorer;
0255     } else {
0256         /* Return stub is in 32bit vsyscall page */
0257         if (current->mm->context.vdso)
0258             restorer = current->mm->context.vdso +
0259                 vdso_image_32.sym___kernel_sigreturn;
0260         else
0261             restorer = &frame->retcode;
0262     }
0263
0264     if (!user_access_begin(frame, sizeof(*frame)))
0265         return -EFAULT;
0266
0267     unsafe_put_user(sig, &frame->sig, Efault);
0268     unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
0269     unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
0270     unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
0271     /*
0272      * These are actually not used anymore, but left because some
0273      * gdb versions depend on them as a marker.
0274      */
0275     unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
0276     user_access_end();
0277
0278     /* Set up registers for signal handler */
0279     regs->sp = (unsigned long) frame;
0280     regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
0281
0282     /* Make -mregparm=3 work */
0283     regs->ax = sig;
0284     regs->dx = 0;
0285     regs->cx = 0;
0286
0287     loadsegment(ds, __USER32_DS);
0288     loadsegment(es, __USER32_DS);
0289
0290     regs->cs = __USER32_CS;
0291     regs->ss = __USER32_DS;
0292
0293     return 0;
0294 Efault:
0295     user_access_end();
0296     return -EFAULT;
0297 }
0298
0299 int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
0300             compat_sigset_t *set, struct pt_regs *regs)
0301 {
0302     struct rt_sigframe_ia32 __user *frame;
0303     void __user *restorer;
0304     void __user *fp = NULL;
0305
0306     /* unsafe_put_user optimizes that into a single 8 byte store */
0307     static const struct {
0308         u8 movl;
0309         u32 val;
0310         u16 int80;
0311         u8  pad;
0312     } __attribute__((packed)) code = {
0313         0xb8,
0314         __NR_ia32_rt_sigreturn,
0315         0x80cd,
0316         0,
0317     };
0318
0319     frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
0320
0321     if (!user_access_begin(frame, sizeof(*frame)))
0322         return -EFAULT;
0323
0324     unsafe_put_user(sig, &frame->sig, Efault);
0325     unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
0326     unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
0327
0328     /* Create the ucontext.  */
0329     if (static_cpu_has(X86_FEATURE_XSAVE))
0330         unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
0331     else
0332         unsafe_put_user(0, &frame->uc.uc_flags, Efault);
0333     unsafe_put_user(0, &frame->uc.uc_link, Efault);
0334     unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
0335
0336     if (ksig->ka.sa.sa_flags & SA_RESTORER)
0337         restorer = ksig->ka.sa.sa_restorer;
0338     else
0339         restorer = current->mm->context.vdso +
0340             vdso_image_32.sym___kernel_rt_sigreturn;
0341     unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
0342
0343     /*
0344      * Not actually used anymore, but left because some gdb
0345      * versions need it.
0346      */
0347     unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
0348     unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
0349     unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
0350     user_access_end();
0351
0352     if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
0353         return -EFAULT;
0354
0355     /* Set up registers for signal handler */
0356     regs->sp = (unsigned long) frame;
0357     regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
0358
0359     /* Make -mregparm=3 work */
0360     regs->ax = sig;
0361     regs->dx = (unsigned long) &frame->info;
0362     regs->cx = (unsigned long) &frame->uc;
0363
0364     loadsegment(ds, __USER32_DS);
0365     loadsegment(es, __USER32_DS);
0366
0367     regs->cs = __USER32_CS;
0368     regs->ss = __USER32_DS;
0369
0370     return 0;
0371 Efault:
0372     user_access_end();
0373     return -EFAULT;
0374 }